The present invention relates to a technical field of an image reader, for photoelectrically reading an image photographed on a film, etc., utilized in a digital photo printer or the like for obtaining a print (a photograph) on which this image is reproduced.
What has hitherto been a dominant exposure used for printing on a photosensitive material (photographic printing paper) an image photographed on a photographic film such as a negative film and a reversal film, etc. (which are simply referred to as a film), is a so-called direct exposure (an analog exposure) in which the image on the film is projected upon the photosensitive material, and the surface of the photosensitive material is exposed to the light.
By contrast, there has been utilized in recent years a printing apparatus using a digital exposure, i.e., a digital photo printer for photoelectrically reading an image recorded on a film, converting the read image into digital signals, thereafter converting the digital signals into image data for recording by executing a variety of image processes thereon, recording the (latent) image by scan-exposing a photosensitive material to recording light beams modulated corresponding to the image data, and obtaining a (finished) print.
The digital photo printer is capable of determining an exposure condition when in printing through image data processing with the image as a digital image data and therefore capable of obtaining a high grade print, which could not acquired by the conventional direct exposure, by preferably compensating a washed-out highlight and a dull shadow of the image which are caused due to the back-light and the flash photography, etc., executing a sharpness (sharpening) process and compensating a color or density failure. The digital photo printer is also capable of synthesizing a plurality of images and dividing the image and further synthesizing characters and so on by the image data processing, and capable of outputting the prints freely edited and processed according to applications.
Besides, the digital photo printer is capable of supplying a computer, etc. with the image data and storing a recording medium such as a floppy disk, etc. with the image data as well as outputting the images as a print (a photograph), and hence the image data can be utilized for a variety of applications excluding the photographs.
This type of digital photo printer is basically constructed of an image input device having a scanner (an image reader) and an image processor, and an image output device having a printer (an image reader) and a processor (a developing unit).
The scanner, with reading light beams emitted from a light source being incident upon a film, obtains projection light beams bearing an image photographed on the film, forms the image of the projection light beams on an image sensor such as CCD sensor, etc. through an image forming lens, then effects a photoelectric conversion thereof, thus reads the image, executes various image processes thereon according to the necessity, and thereafter transmits image data (image data signals) of the film to the image processor.
The image processor sets an image processing condition based on the image data read by the scanner, executes an image process corresponding to the set condition on the image data, and transmits output image data (an exposure condition) for recording the image.
The printer, if classified as a device utilizing, e.g., a light beam scan exposure, modulates the light beams in accordance with the image data transmitted from the image processor, deflects the light beams in a main scan direction, then carries a photosensitive material in a sub-scan direction orthogonal to the main scan direction, forms a latent image by exposing (printing) the photosensitive material to the light beams bearing the image, subsequently executes a development process, etc. corresponding to the photosensitive material with the aid of the processor, and obtains a print (a photograph) on which the image photographed on the film is reproduced.
The image reader using the image sensor such as the CCD described above, however, exhibits a low resolution, and it has been therefore desired that the resolution be enhanced. What is contrived in contrast is, for instance, a method by which the pixels are shifted in vertical and lateral directions utilizing the piezoelectric effect by use of an area sensor such as an area CCD sensor, thereby quadrupling the resolution. This method of shifting the pixels of the area sensor, however, presents a problem in which the operation thereof becomes troublesome, and the cost increases.
It is a primary object of the present invention, which was devised to obviate the problems inherent in the prior art, to provide an image reader capable of increasing a resolution while simply keeping an area of light receiving elements of a sensor to some extent at a low cost.
To accomplish the above object, according to one aspect of the present invention, an image reader comprises n pieces of line sensors arranged in parallel in such a way that, with xe2x80x9cnxe2x80x9d being an integer of 2 or more, the n pieces of line sensors disposed at an equal pitch are shifted at a 1/n pitch in a sensor arranging direction with respect to other line sensors, first compensating means for compensating spatial positions of the n pieces of line sensors, second compensating means for compensating a train of signals of each of the n pieces of line sensors so that a predetermined moving average of a target pixel of the signal train in one line sensor is, in a signal train of another line sensor among the n pieces of line sensors, coincident with a predetermined moving average of a target pixel corresponding to the target pixel in the one line sensor, and interleaving means for interleaving the n trains of signals which have been compensated by the second compensating means.
According to another aspect of the present invention, an image reader comprises two line sensors arranged in parallel in such a way that a first line sensor of the two line sensors disposed at an equal pitch is shifted at half a pitch in a sensor arranging direction with respect to another line sensor, first compensating means for compensating spatial positions of the two line sensors, second compensating means for compensating a train of signals of each of the two line sensors so that a predetermined moving average of a target pixel of the signal train in the first line sensor of the two line sensors is, in a signal train of a second line sensor, coincident with a predetermined moving average of a target pixel corresponding to the target pixel in the one line sensor, and interleaving means for interleaving the two trains of signals which have been compensated by the second compensating means.
It is preferable that the two line sensors include the same optical filter on-sensor front surfaces.
When the moving average of the target pixel in the first line sensor is made, in the signal train of the second line sensor, coincident with the moving average of the target pixel corresponding to the target pixel in the first line sensor, the moving average with a smaller signal value is a basis to be made coincident with.
It is also preferable that the two line sensors transfer pixel signals in direction opposite to each other.
It is further preferable that four line sensors are structured such that in respective channels for three colors of R, G and B, the two line sensors are provided with respect to only the G-channel, a line sensor is provided with respect to each of R- and B-channels.
Other features and advantages of the present invention will become readily apparent from the following description taken in conjunction with the accompanying drawings.